Tracking ocean eddies with AIS

Almost all ships nowadays are equipped with an Automatic Identification System (AIS), primarily to improve marine traffic safety. The system broadcasts signals containing the ship’s identity, location, speed, heading and more every 2-10 seconds. These signals, collected and stored, make it possible to track the voyages of individual ships and to create time series of their movements. With the help of a simple parametric model, variations in the ship’s speed time series can be related to the wind, wave, and current conditions that are encountered during the voyage. One application of this model, to make forecasts of a ship’s speed in order to improve the arrival time estimate, was discussed earlier (ship arrival times). Here we consider the potential of using AIS time series to assess surface currents, turning ships into moving buoys.